I explore regions beyond "rules", Van's will answer questions outside the standard windows, but you may have to wait since not as many are dedicated to phone support.
To the OP, I have not run wires down there for that reason. Mine are either under the rails, or down the center. I even found (here on VAF) that additional holes have been factory approved to be drilled in the spar. Stresswise, holes in the neutral axis won't weaken the beam, but I wouldn't w/o consulting the factory.